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Java Forum / First Aid / February 2006

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Canvas Double Buffering - help!

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dontspam@_dylan_.gov - 04 Feb 2006 22:25 GMT
Hi all, I need some double-buffering help...

I have created an applet, which has a paint() method. There is also a derived Canvas class I made ("PlotCanvas"). The applet draws two

instances of these, each with its own paint() method. So, I tried following the instructions here:

http://www.realapplets.com/tutorial/DoubleBuffering.html

But I get problems in paint(), since calling getGraphics() returns NULL. Even when I check for NULL, and skip painting until

getGraphics() doesn't return NULL... it never doesn't return NULL. I can give more details if need be. This a common problem?

Thanks!
Roedy Green - 05 Feb 2006 00:37 GMT
>But I get problems in paint(), since calling getGraphics() returns NULL. Even when I check for NULL, and skip painting until
>getGraphics() does

you are not supposed to call getGraphics. AWT is supposed to pass a
Graphics object to your paint method.
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Canadian Mind Products, Roedy Green.
http://mindprod.com Java custom programming, consulting and coaching.

Knute Johnson - 05 Feb 2006 01:59 GMT
>> But I get problems in paint(), since calling getGraphics() returns NULL. Even when I check for NULL, and skip painting until
>> getGraphics() does
>
> you are not supposed to call getGraphics. AWT is supposed to pass a
> Graphics object to your paint method.

He is confused but he does need to call getGraphics() on his buffer image.

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Knute Johnson
email s/nospam/knute/



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